1. Field of the Technology
This invention relates generally to magnetic heads of magnetic storage devices such as disk drives, and more particularly to magnetic heads having extraordinary magnetoresistance (EMR) sensors.
2. Description of the Related Art
Magnetoresistive (MR) sensors have typically been used as read sensors in hard disk drives. An MR sensor detects magnetic field signals through the resistance changes of a read element, fabricated of a magnetic material, as a function of the strength and direction of magnetic flux being sensed by the read element. The conventional MR sensor, such as that used as a MR read head for reading data in magnetic recording disk drives, operates on the basis of the anisotropic magnetoresistive (AMR) effect of the bulk magnetic material, which is typically permalloy. A component of the read element resistance varies as the square of the cosine of the angle between the magnetization direction in the read element and the direction of sense current through the read element. Recorded data can be read from a magnetic medium, such as the disk in a disk drive, because the external field from the recorded magnetic medium (the signal field) causes a change in the direction of magnetization in the read element, which causes a change in resistance of the read element and a resulting change in the sensed current or voltage. Other types of sensors, such as GMR sensors and tunnel valve sensors, also utilize magnetic materials for operation.
Today's sensors are becoming very small, with trackwidths (TWs) approaching between about 50-200 nanometers (nm). With increasing areal densities and advancements in electron beam (e-beam) lithography, the trackwidth may shrink even below 50 nm. Given such reduced sizes, conventional sensors increasingly suffer from magnetic noise. In particular, the volume of a free layer of the sensor needs to be reduced in accordance with the trackwidth. However, a reduced volume makes the free layer magnetization more susceptible to thermal agitation, which leads to magnetic noise. Therefore, a sensor made from non-magnetic materials may be desirable for detecting small magnetic excitations such as those found in an ultrahigh-density disk drive.
A recently recognized type of semiconductor material exhibits extraordinary magnetoresistance (EMR). While such semiconductor material has been recognized as a candidate for use in storage technology, there have been minimal advancements in actual implementations of such application. The different characteristics exhibited by the EMR material with respect to traditional materials used with MR magnetic heads represent one reason for this lack of advancement. In particular, the MR magnetic heads can not simply be substituted with EMR magnetic heads. EMR magnetic heads require the signal field to be perpendicular to a field receiving surface of the magnetic head to achieve the EMR effect.
Accordingly, there is a need to solve this implementation issue so that EMR magnetic heads may be suitable for use in magnetic recording disk drives or any other desired storage technology context.